If Mohamed Salah's injury is serious, it wouldn't be good for Liverpool. Losing their best players in a mid-season African Cup will end their leadership joy. Hamstring injuries can be serious.
The moment Liverpool make a mistake, Manchester City take the lead and never let it go. From then on, the balance in the Premier League will not change easily. City had given other teams enough advances. Liverpool and Arsenal couldn't use this well. They needed to collect more points. City with De Bruyne won't lose points easily anymore.
Salah is Liverpool's best player at the moment. Not only is he good at scoring goals and looking for opportunities, but he also has extraordinary assist and pre-assist abilities. He can create opportunities for himself or open up space for other players. I often see how Salah is able to draw 1 or 2 defenders towards himself thereby opening up space for other players. And he is also good at positioning himself on the field to create opportunities. I think Salah's injury will have a big impact on Liverpool who are leading the standings with only 2 points difference from City.